Plasma separator assembly having interface-seeking piston with centrifugal valve

ABSTRACT

A blood collection and separator assembly of the type suitable for centrifuging to separate the plasma or serum from the cellular phase of blood is disclosed. The assembly includes a collection container and an interface-seeking piston having a centrifugal valve associated therewith being slidably disposed therein for opening the valve during centrifugation and for sealing off the plasma or serum phase from the cellular or heavy phase of blood after centrifuging is terminated. The piston is formed having a specific gravity greater than the specific gravity of blood. The piston is provided with a valve assembly which automatically opens the valve when the assembly is subjected to centrifugal force. Disposed in tandem relationship with the valve means is a filter assembly to filter the plasma or serum as it passes through the valve means when the assembly is being centrifuged and the piston is moving downwardly into the container. The piston automatically stops at the plasma/serumcellular interface by clogging the filter assembly with the cellular phase. When the centrifugal force is terminated the valve means is closed and the piston forms a barrier between the plasma or serum phase and the cellular phase.

United States Patent Ayres INTERFACE-SEEKING PISTON WITH CENTRIFUGALVALVE PLASMA SEPARATOR ASSEMBLY HAVING [75] Inventor: Waldemar A. Ayres,Rutherford,

[73] Assignee: Becton, Dickinson and Company,

East Rutherford, NJ.

[ Notice: The portion of the term of this patent subsequent to July 15,1992, has been disclaimed.

[22] Filed: Feb. 27, 1974 [21] Appl. No.: 446,370

[52] US. Cl. 210/136; 210/314; 210/359;

210/516; 210/DIG. 23

[51] Int. Cl B01d 21/26 [58] Field of Search 23/230 B, 258.5, 259, 292;

128/2 F, 214 R, 218 M, 272; 210/83, 84, 109,131, 359, 514-518, DIG. 23,DIG. 24,

Primary Examiner-John Adee Assistant EraminerRobert H. Spitzer Attorney,Agent, or Firm-Kane, Dalsimer, Kane, Sullivan and Kurucz [57] ABSTRACT Ablood collection and separator assembly of the type suitable forcentrifuging to separate the plasma or serum from the cellular phase ofblood is disclosed. The assembly includes a collection container and aninterface-seeking piston having a centrifugal valve associated therewithbeing slidably disposed therein for opening the valve duringcentrifugation and for sealing off the plasma or serum phase from thecellular or heavy phase of blood after centrifuging is terminated. Thepiston is formed having a specific gravity greater than the specificgravity of blood. The piston is provided with a valve assembly whichautomatically opens the valve when the assembly is subjected tocentrifugal force. Disposed in tandem relationship with the valve meansis a filter assembly to filter the plasma 136, 314, 316', 233/1 A, l R,26 or serum as it passes through the valve means when the assembly isbeing centrifuged and the piston is [56] References Cited movingdownwardly into the container. The piston au- UNITED STATES PATENTStomatically stops at the plasma/serum-cellular inter- 2,577,7s0 12/1951Lockhart 128/272 X face by cloggmg the filter assembly.wlth T cellular 3539 300 11/1970 Stone n ZIO/DIG. 24 phase. When the centrifugal force 18terminated the 3:647:07) 3/1972 Adler I l 210/83 valve means is closedand the piston forms a barrier 3,661,265 5/1972 Greenspan 210/359between the plasma or Serum Phase and the cellular 3,741,400 6/1973 Dick2lO/DIG. 23 phase. 3,782,548 1/1974 Bowen 2l0/D1G. 23

6 Claims, 2 Drawing Figures IO "T= 1::

1 PLASMA SEPARATOR ASSEMBLY HAVING INTERFACE-SEEKING PISTON WITHCENTRIFUGAL VALVE BACKGROUND OF THE INVENTION This inventionplasma/serum generally to plasma/- serum separator assemblies andparticularly to a plasma/serving separator having an interface-seekingpiston with a centrifugal valve assembly. The piston is slidablydisposed in a collection container for receiving blood. The pistonincludes valve means which is normally closed but which willautomatically open when the assembly is subjected to centrifugal force.The piston also includes a filter means disposed in fluid communicationwith the valve means so that as the plasma or serum passes through thevalve means it is filtered to remove any solid materials that may bepresent in the plasma or serum phase and which provides means forstopping the piston at the interface between the serum/plasma andcellular phase.

DESCRIPTION OF THE PRIOR ART It is known to separate blood into itscomponent parts by centrifugation, for example, the assembly disclosedin U.S. Pat. No. 2,460,641. However, this particular assembly does notemploy a means for sealing the separated plasma or serum phase from thecellular phase.

It is also known to provide assemblies for manually separating theplasma or serum phase from the cellular phase, for example, as disclosedin U.S. Pat. Nos. 3,586,064; 3,661,265; 3,355,098; 3,481,477; 3,512,940and 3,693,804. In all of these devices the serum is collected in a bloodcollection container and means are provided for separating the plasma orserum phase from the cellular phase employing filters, valves, transfertubes or the like.

It is also known to provide assemblies for the sealed separation ofblood in which a piston is actuated by centrifugal force such as isdisclosed in US. Pat. Nos. 3,508,653 and 3,779,383. These devices useeither a deformable piston made of a resilient material or valve meansassociated with the piston to effect a sealed separation aftercentrifugation.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a plasma/serum separator assembly in which an interface-seekingpiston automatically stops when centrifuged at the plasma/serum-cellularinterface.

It is another object of the invention to provide a piston having acentrifugal valve means that will not be accidentally opened when thecontainer is being filled with blood by the pressure difference of bloodat atmospheric pressure and the vacuum on the other side of the valve.It is also an object of the invention to provide a piston having afilter assembly which will prevent cellular materials contained in theblood from passing into the separated plasma or serum phase.

It is another object of the invention to provide a plas ma/serumseparator assembly which is economical to manufacture and can be used inconjunction with standard blood collecting equipment.

My invention generally contemplates the provision of a separatorassembly which includes a blood collection container for receivingblood, the container having at least one open end which is adapted toreceive a closure for sealing the end of the container. Aninterfaceseeking piston is formed having a specific gravity greater thanthe specific gravity of blood and having a centrifugal valve means whichautomatically opens when the assembly is subjected to centrifugal force.A filter assembly is disposed in the piston in fluid communication withthe valve means so that the plasma and/or serum after passing throughthe valve means is filtered to remove any solid materials containedtherein. The piston automatically stops when the filter assembly becomesclogged with the heavy phase at the plasma/- serum-cellular interface.

DESCRIPTION OF THE DRAWINGS For a better understanding of the inventionreference is had to the drawings which illustrate a preferred embodimentof the invention herein.

FIG. 1 is a sectional, elevational view of the plasma/- serum separatorassembly illustrating a pointed cannula penetrating one of the stopperedends of the container through which blood is introduced into thecontainer prior to its separation.

FIG. 2 is an enlarged sectional, elevational view partly broken awayillustrating the position of the piston approaching theplasma/serum-cellular interface while the assembly is being centrifuged.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding ofthe invention herein a description of the preferred embodiment is hadwhich is illustrated in FIGS. 1 and 2.

In FIG. 1 separator assembly 10 comprises a tubular member or container12 which is sealed at its open ends by closure members 14 and 15.Closure members 14 and 15 are preferably made of elastomeric material,for example, rubber, and are capable of being penetrated by a cannula 16so that blood can be transferred from a blood source into the containerunder aseptic conditions. Closures 14 and 15 should be self-sealing sothat when the cannula is removed from closure 14 there will be no lossof blood passing through the penetration portion of closure 14. Asdepicted in FIG. 1, blood is being conducted through cannula l6 and isshown filling container 12 to about the point where piston 18 ispositioned adjacent closure member 15. Thereafter, cannula 16 is removedand assembly 10 is ready for centrifuging for subsequent separation ofthe collected blood into the plasma or serum phase and the cellularphase. In this connection, apertures 37 of diaphragm 36 remain closedwhile blood is filling container 12 and will not accidentally open bythe pressure differential between blood at atmospheric pressure and thevacuum that is present in the filter 40 and at the top surface ofdiaphragm 36.

Disposed in container 12 is piston 18 which includes a tubular metalinsert 22 which is mounted in the annular recess 23 of piston 18. Metalinsert 22 is preferably made of stainless steel or other rigidchemically inert material having a specific gravity substantiallygreater than blood. The body of piston 18 is preferably formed ofelastomeric material and is provided with annular recess 23 which isdimensioned to receive tubular member 22 in an interference fit so thatno air space remains in annular recess 23.

The elastomeric portion of piston 18 comprises an outer wall 26 andspaced therefrom is inner wall 28 in which their respective wallsurfaces define annular recess 23. Formed integrally with wall 26 is aplurality of radially spaced resilient sealing rings 30 which contactthe inner wall surface of container 12 in sealing liquidtightengagement. Piston 18 when mounted in the container will maintain aliquidtight sealing contact with the inner wall of container 12throughout the pistons path of travel within the container duringcentrifuging. A longitudinally extending bore 32 provides a chamber forhousing filter assembly 40. Valve means 34 includes a resilientdiaphragm 36 and weighted mass 39. Diaphragm 36 is formed across thelower end of piston 18 to provide a barrier or closure for bore 32 andis made of a suitable elastomer, for example rubber. Also, positionedadjacent valve means 34, in bore 32, is filter assembly 40. Positionedwithin bore 32 and contacting the inner face of diaphragm 36 is aweighted mass or tubular insert 39 preferably cylindrical and having adiameter substantially less than the diameter of bore 32 which providescentrifugal valve opening means for diaphragm 36. Mass 39 has a loosefit relative to filter assembly 40. When the blood separator assembly iscentrifuged to effect separation of the cellular phase from the plasmaor serum phase, mass 39 presses against diaphragm 36 with sufficientforce to stretch diaphragm 36 downwardly to thereby open apertures 37.

As shown in FIG. 2, filter assembly 40 includes coarse filter 42 whichis mounted in bore 32 of piston 18 and fine filter 44 which is securedwith a suitable adhesive on to piston 18 so that it covers the upperopening of bore 32. Filter 42 has an interference fit relative to bore32 so that filter 42 remains in fixed position. Diaphragm 38 is alsomade of a suitable elastomer, for example rubber, and is cemented orotherwise secured to the top of wall 26 of piston 18. Diaphragm 38 isformed having one or more apertures or slits which are normally closedbut which are opened when plasma/serum is passing through piston 18 asillustrated by the direction of the arrows in FIG. 2.

Fine filter 44 has average pore openings less than the average diameterof the red blood cells so that any plasma or serum containing solidmaterials of the diameter of a red blood cell or larger will be removedby filter 44 before passing through apertures 39 of diaphragm 38. Coarsefilter 42 has an average pore size greater than the cellular phase ofblood and serves as a prefilter to take out larger particles such asfibrin strands or clots from the plasma or serum before it reaches finefilter 44.

FIG. 2, which is an enlarged sectional view partly broken away,illustrates the position of piston 18 approaching theplasma/serum-cellular interface 50 during centrifugation and before thecells pass through coarse filter 42 and clog fine filter 44 therebystopping the descent of piston 18 at the interface. It should be notedthat apertures 37 and 41 of diaphragms 36 and 38 are open during thedescent of piston 18 in container 12 but apertures 41 will automaticallyclose when fine filter 44 clogs with red cells while apertures 37 ofdiaphragm 36 remain open even though centrifuging continues. Whencentrifuging ceases apertures 37 of diaphragm 36 will automaticallyclose. It should be noted that piston 18 has a specific gravitysubstantially greater than the specific gravity of blood. However,piston 18 will automatically stop at the plasma/- serum-cellularinterface 50 when filter 44 of piston 18 becomes clogged with the heavycellular phase, such as the red blood cells, thereby separating thelight phase plasma or serum from the heavy phase cellular material ofblood and will form a barrier between the two phases when centrifugingis completed.

When using the assembly illustrated in FIGS. 1 and 2 after the blood hasbeen collected, assembly 10 is placed in a centrifuge and, at first, issubjected to a spin speed which is suitable to cause the heavy orcellular phase material to pass downwardly in the container towardstopper 14 but the spin speed is insufficient to cause the piston 18 toslide downwardly through the plasma/serum phase. Then, the assembly issubjected to a higher spin speed which causes mass 39 to pressdownwardly on diaphragm 36 additionally to open apertures 37 in piston18. Piston 18 then starts its movement downwardly in the container andseparated plasma or serum pass through apertures 37 and through coarsefilter 42 and fine filter 44. The hydrostatic pressure of theplasma/serum exerted against diaphragm 38 causes it to stretch upwardlythereby opening valve apertures 41 to permit the passage of separatedplasma or serum to the top side of piston 18. When piston 18 reaches theplasma/serum-cellular interface, red cells and other portions of thecellular phase pass through coarse filter 42 and are stopped by finefilter 44 thereby causing filter 44 to become clogged and effectivelystop piston 18 at the plasma/serum-cellular interface 50. Thereafter,even though centrifuging continues diaphragm 38 returns to its normalrelaxed position as in FIG. 1 with apertures 41 closed. However, untilcentrifuging ceases apertures 37 of diaphragm 36 remain open due to mass39 exerting a force against diaphragm 36. When centrifuging ceases,resilient diaphragm 36 moves mass 39 to its normal position therebyautomatically closing apertures 37. When centrifuging is completed thepiston is established as a sealed barrier at the interface between theserum/plasma phase and the cellular phase.

From the foregoing, it is readily observed that a plasma/serum separatorassembly in which an interfaceseeking piston with a centrifugal valve isdisclosed the assembly is described in which blood can be collected,centrifuged, separated into its component phases and is capable of beingshipped through the mail for further analytical determinations withoutthe plasma or serum mixing with the cellular phase even though theassembly is inverted and handled roughly.

While variations of the invention herein may be had the objectives ofthe invention have been illustrated and described and it is contemplatedthat changes in design can be made without departing from the spirit ofthe invention described herein.

What is claimed is:

1. A separator assembly capable of separating blood into a plasma/serumor light phase and a cellular or heavy phase comprising:

a container having at least one open end which is adapted to receiveblood for subsequent separation into a light phase and a heavy phase;

a closure sealing the open end of the container, the closure beingformed of a self-sealing, elastomeric material which is penetrable by acannula through which blood to be separated is conducted into thecontainer;

an interface-seeking piston having a specific gravity relatively greaterthan blood and slidably mounted in the container adjacent one endthereof and being movable downwardly in said container due to theinfluence of centrifugal force and having means on an outer surface forproviding sealing engagement with an inner surface of the container;

a valve assembly mounted on the piston and disposed at the lower endthereof, said assembly comprises a lower resilient diaphragm mounted onthe lower end of said piston and having apertures formed therein, saidapertures being normally closed and adapted to open during the downwardmovement of the piston; an upper resilient diaphragm mounted on theupper end of said piston, having apertures formed therein, saidapertures being normally closed and adapted to open during the downwardmovement of the piston;

a filter assembly mounted between said valve assembly and said upperdiaphragm and being in fluid communication with the valve assembly, saidfilter assembly including a lower coarse filter having an average poreopening larger than the diameter of blood cells, disposed adjacent saidvalve assembly and an upper fine filter having an average pore openingsmaller than the diameter of blood cells, said fine filter disposedbetween the upper diaphragm and said coarse filter, said filter assemblybeing capable of removing substantially all solid material from theseparated plasma/serum phase; and

said fine filter providing piston stop means when said piston is at theplasma/serum-cellular interface whereby the cellular phase clogs thefine filter to prevent further upward flow of fluid through the finefilter so that the piston automatically stops at said interface and theupper diaphragm apertures close.

2. The separator assembly of claim 1 wherein the valve assembly includesa weight mass disposed on the upper surface of said lower diaphragm,said mass being forced downward against the lower resilient diaphragmwhen the assembly is subjected to centrifugal force whereby said lowerdiaphragm is stretched and the apertures therein are opened.

3. The separator assembly of claim 1 wherein said filter assembly isdisposed in a passage formed through said piston, the upper and lowerends of said passage being closed by said upper and lower resilientdiaphragms respectively.

4. An interface-seeking piston adapted for use for separating the serumor plasma phase from the cellular phase of blood in a separator assemblyincluding a container, said piston having a specific gravity relativelygreater than blood and adapted to be slidably mounted adjacent one endof the container and movable downwardly in said container due to theinfluence of centrifugal force and having means on an outer surfacethereof for providing sealing engagement with an inner surface of thecontainer;

a valve assembly mounted on the piston and disposed at the lower endthereof, said assembly comprises a lower resilient diaphragm mounted onthe lower end of said piston and having apertures therein, saidapertures being normally closed and adapted to open during the downwardmovement of the piston;

a resilient upper diaphragm having apertures formed therein and mountedat the upper end of said piston with said apertures being normallyclosed and adapted to open during the downward movement of the piston;

a filter assembly mounted between said valve assembly and said upperdiaphragm and being in fluid communication with the valve assembly, saidfilter assembly including a lower coarse filter having an average poreopening larger than the cellular phase, disposed adjacent said valveassembly and an upper fine filter having an average pore opening smallerthan cellular phase; said fine filter disposed between said upperdiaphragm and said coarse filter, said filter assembly being capable ofremoving substantially all solid material from the separatedplasma/serum phase and said fine filter being adapted to provide pistonstop means when said piston is at the plasma/serum-cellular interface.

5. The piston of claim 4 wherein the valve assembly includes aweight-mass disposed on the upper surface of said lower diaphragm, saidmass being forced downward against the resilient lower diaphragm whenthe piston is subjected to centrifugal force whereby said lowerdiaphragm is stretched and the apertures therein are opened.

6. The piston of claim 4 wherein said filter assembly is disposed in apassage formed through said piston, the upper and lower ends of saidpassage being closed by said upper and lower resilient diaphragmsrespectively.

1. A SEPARATOR ASSEMBLY CAPABLE OF SEPARATING BLOOD INTO A PLASMA/SERUMORLIGHT PHASE AND A CELLULAR OR HEAVY PHASE COMPRISING: A CONTAINERHAVING AT LEAST ONE OPEN ND WHICH IS ADAPTED TO RECEIVE BLOOD FORSUBSEQUENT SEPARATION INTO A LIGHT PHASE AND A HEAVY PHASE, A CLOSURESEALING THE OPEN END OF THE CONTAINER, THE CLOSURE BEING FORMED OF ASELF-SEALING, ELASTOMERIC MATERIAL EHICH IS PENETRABLE BY A CANNULATHROUGH WHICH BLOOD TO BE SEPARATED IS CONDUCTED INTO THE CONTAINER, ANINTERFACE-SEEKING PISTON HAVING A SPECIFIC GRAVITY RELATIVELY GREATERTHAN BLOOD AND SLIDABLY MOUNTED IN THE CONTAINER ADJACENT ONE ENDTHEREOF AND BEING MOVABLE DOWNWARDLY IN SAID CONTAINER DUE TO HEREFLUENCE OF CENTRIFUGAL FORCE AND HAVING MEANS ON AN OUTER SURFACE FORPROVIDING SEALING ENGAGEMENT WITH AN INNER SURFACE OF THE CONTAINER, AVALVE ASSEMBLY MOUNTED ON THE PISTON AND DISPOSED AT THE LOWER ENDTHEREOF, SAID ASSEMBLY COMPRISES A LOWER RESILIENT DIAPHRAGM MOUNTED ONTHE LOWER END OF SAID PISTON AND HAVING APERTURES FORMED THEREIN, SAIDAPERTURES BEING NORMALLY CLOSED AND ADAPTED TO OPEN DURING THE DOWNWARDMOVEMENT OF THE PISTON, AN UPPER RESILIENT DIAPHRAGM MOUNTED ON THEUPPER END OF SAID PISTON, HAVING APERTURES FORMED THEREIN, SAIDAPERTURES BEING NORMALLY CLOSED AND ADAPTED TO OPEN DURING THE DOWNWARDMOVEMENT OF THE PISTON, A FILTER ASSEMBLY MOUNTED BETWEEN SAID VALVEASSEMBLY AND SAID UPPER DIAPHRAGM AND BEING IN FLUID COMMUNICATION WITHTHE VALVE ASSEMBLY, SAID FILTER ASSEMBLY INCLUDING A LOWER COARSE FILTERHAVING AN AVERAGE PORE OPENING LARGER THAN THE DIAMETER OF BLOOD CELLS,DISPOSED ADJACENT SAID VALVE ASSEMBLY AND AN UPPER FINE FILTER HAVING ANAVERAGE PORE OPENING SMALLER THAN THE DIAMETER OF BLOOD CELLS, SAID FINEFILTER DISPOSED BETWEEN THE UPPER IAPHRAGM SAID SAID COARSE FILTER, SAIDFILTER ASSEMBLY BEING CAPABLE OF REMOVING SUBSTANTIALLY ALL SOLIDMATERIAL FROM THE SEPARATED PLASMA/SERUM PHASE, AND SAID FINE FILTERPROVIDING PISTON STOP MEANS WHEN SAID PISTON IS AT THEPLASMA/SERUM-CELLULAR INTERFACE WHEREBY THE CELLULAR PHASE CLOGS THEFINE FILTER TO PREVENT FURTHER UPWARD FLOW OF FLUID THROUGH THE FINEFILTER SO THAT THE PISTON AUTOMATICALLY STOPS AT SAID INTERFACE AND THEUPPER DIAPHRAGM APERTURES CLOSE.
 2. The separator assembly of claim 1wherein the valve assembly includes a weight mass disposed on the uppersurface of said lower diaphragm, said mass being forced downward againstthe lower resilient diaphragm when the assembly is subjected tocentrifugal force whereby said lower diaphragm is stretched and theapertures therein are opened.
 3. The separator assembly of claim 1wherein said filter assembly is disposed in a passage formed throughsaid piston, the upper and lower ends of said passage being closed bysaid upper and lower resilient diaphragms respectively.
 4. Aninterface-seeking piston adapted for use for separating the serum orplasma phase from the cellular phase of blood in a separator assemblyincluding a container, said piston having a specific gravity relativelygreater than blood and adapted to be slidably mounted adjacent one endof the container and movable downwardly in said container due to theinfluence of centrifugal force and having means on an outer surfacethereof for providing sealing engagement with an inner surface of thecontainer; a valve assembly mounted on the piston and disposed at thelower end thereof, said assembly comprises a lower resilient diaphragmmounted on the lower end of said piston and having apertures therein,said apertures being normally closed and adapted to open during thedownward movement of the piston; a resilient upper diaphragm havingapertures formed therein and mounted at the upper end of said pistonwith said apertures being normally closed and adapted to open during thedownward movement of the piston; a filter assembly mounted between saidvalve assembly and said upper diaphragm and being in fluid communicationwith the valve assembly, said filter assembly including a lower coarsefilter having an average pore opening larger than the cellular phase,disposed adjacent said valve assembly and an upper fine filter having anaverage pore opening smaller than cellular phase; said fine filterdisposed between said upper diaphragm and said coarse filter, saidfilter assembly being capable of removing substantially all solidmaterial from the separated plasma/serum phase and said fine filterbeing adapted to provide piston stop means when said piston is at theplasma/serum-cellular interface.
 5. The piston of claim 4 wherein thevalve assembly includes a weight-mass disposed on the upper surface ofsaid lower diaphragm, said mass being forced downward against theresilient lower diaphragm when the piston is subjected to centrifugalforce whereby said lower diaphragm is stretched and the aperturestherein are opened.
 6. The piston of claim 4 wherein said filterassembly is disposed in a passage formed through said piston, the upperand lower ends of said passage being closed by said upper and lowerresilient diaphragms respectively.